Colorimetric determination of somatic cell count in milk

Abstract

The invention involves using a simple colorimetric method for a quantitative test to measure white blood cells in milk samples. The invention includes a new reagent system, a new analysis method, and a new apparatus which permits in-line colorimetric analysis.

1 . A reagent system for the colorimetric determination of somatic cell count in milk comprising a dye substrate that can be hydralized by the esterase on white blood cells to form a colored dye dissolved in a low molecular weight alcohol and a buffer in concentrations between 0.01 M to 2M and adapted to maintain the system at a pH in the range of 7.0 to 11.0. 
     
     
         2 . A reagent system in accordance with  claim 1  additionally including a surfactant capable of dispersing the cell components of milk in an assay mixture. 
     
     
         3 . A reagent system in accordance with  claim 1  in which said reagent system consists of a mixture of said dye substrate and said buffer. 
     
     
         4 . A reagent system in accordance with  claim 2  in which said reagent system consists of a mixture of said dye substrate and said buffer and in which said surfactant is admixed with said dye substrate and said buffer. 
     
     
         5 . A method for the determination of the somatic cell count in milk comprising mixing a milk sample to be analyzed with a reagent system for the colorimetric determination of somatic cell count in milk comprising a dye substrate that can be hydralized by the esterase on white blood cells to form a colored dye dissolved in a low molecular weight alcohol and a buffer in concentrations between 0.01 M to 2M and adapted to maintain the system at a pH in the range of 7.0 to 11.0, and measuring the colorimetric change in the milk sample. 
     
     
         6 . A method in accordance with  claim 4  wherein, said reagent system additionally contains a surfactant capable of dispersing the cell components of milk in an assay mixture. 
     
     
         7 . An apparatus for the in-line colorimetric determination of the somatic cell count in milk comprising in combination a peristaltic pump, a mixing chamber, a supply of dye substrate reagent, a supply of buffer, means for delivering the dye substrate and said buffer to said mixing chamber, a separate means for delivering a milk sample for analysis to said mixing chamber after said substrate and said buffer have been mixed, and means for measuring colorimetric change of the reagent buffer-milk mixture. 
     
     
         8 . An apparatus in accordance with  claim 7  in which said means for measuring the colorimetric change is a means for reading color change by the transmission of light through the sample. 
     
     
         9 . An apparatus in accordance with  claim 7  in which said means for measuring the colorimetric change is a means for reading color change by the reflectance of light from the sample.